|A new movie
for the Annual Insect Fear Film Festival? Unfortunately, not. The Asian longhorned beetle
(Anoplophora glabripennis) is a very real threat.
||The Beetle That Ate
This 1.25-inch long, coal black beetle with irregular white
spots on its back and 2-inch long antennae with white rings has invaded the United States,
including Chicago, and it has a taste for our hardwood trees.
"I had heard about the Asian longhorned beetle when it
was discovered in New York in 1996," says Larry Hanks, assistant professor of
Entomology. "I was interested in learning more about it since I was studying a
related species native to Australia. The Eucalyptus longhorned borer (Phoracantha
semipunctata) has killed millions of eucalyptus trees in California since it was
introduced in the 1980s."
"I thought that within 10 years we might find the
Asian longhorned beetle in Chicago, and then I would have a chance to work on it."
But last summer they were found in Ravenswood and several other areas in Chicago. "I
think the beetles may actually have been in the Chicago area for at least 6 years.
Although this is a flashy looking beetle, it is very hard to see in a tree, and probably
This beetle is a serious pest in its native China where it
kills hardwood trees. "We are fairly certain that the Asian longhorned beetle came to
the United States in wooden shipping pallets from China." And this beetle has a big
"The Asian longhorned beetle prefers maple
species including Norway, red, silver, sugar, and boxelderbut it also attacks
elm, black locust, green ash, mulberry, horse chestnut, poplars, and willows, or more than
60% of our street trees."
"Ironically, these tree species were planted to
replace the elms killed by Dutch elm disease." This new pest may have equally
Although quarantines have been established and efforts are
directed at trying to minimize the beetles spread, "it will be very difficult.
The latitudes in China for its normal range correspond with the area from the Great Lakes
to Cancun, Mexico."
Eradication of this pest is extremely unlikely. There are
no natural predators. The larvae tunnel under the bark and into the wood, perhaps 6 inches
under the surface, so topical insecticides are not effective. Systemic insecticides, even
if effective, would be cost prohibitive. "It is a very pernicious pest."
Of the 35,000 species in this large family of beetles, many
species seem to attack only stressed trees. WPWR Channel 50 Foundation in Chicago has
awarded Hanks a grant to determine if the Asian longhorned beetle also uses stressed trees
"If stress is required for infestation, then the Asian
longhorned beetle probably wont be a forest pest and it may not affect the maple
syrup and tourist industries of the Northeast. Also, home-owners might be able to help
prevent infestation in valuable trees by proper pruning, fertilization, etc."
To measure tree stress, Hanks and his students use a
pressure bomb, a stainless steel chamber with a locking lid. They insert a leaf in the
chamber with the petiole sticking through an opening in the lid. Then they apply pressure
to the chamber until water comes out of the petiole, which is directly related to the
water tension in the leaf. The higher the pressure, the more stressed the tree. After
these baseline studies are conducted, Hanks and his associates will monitor patterns of
infestation to determine whether the beetle prefers stressed treesa process that
will take years.
Hanks is interested in how adult behavior is influenced by
its larval host requirements. Some beetle species feed on dying and dead trees. The
nutritional quality of the host disintegrates quickly and there is intense competition for
"We have found that the adults of such species are
active fliers, quickly moving from tree to tree; adults feed for a short time, mate for
very short periods, and lay eggs quickly."
The Asian longhorned beetle requires a living host.
"As adults they will feed on the leaves, mate for hours, and may never leave their
natal (or birth) tree. The adults are very lethargic. If you knock one out of the tree, it
will just walk back and climb up the tree."
Multiple generations may be found in one tree, and it may
take 5-6 years to kill a host, depending on the level of infestation. Understanding the
beetles behavior may help in suggesting future control strategies.
The introduction of the Asian longhorned beetle into the US
is a consequence of improved trade relations with China.
"Global commerce provides many opportunities for
stow-away pests, and the problem will only get worse. There is a longhorned beetle in
Japan that attacks pine trees. Imagine if it invades the States."
"These exotics are like the AIDS epidemic, and global
shipping is like unprotected sex," says Hanks. "The only good thing is job
securityat least for entomologists."
||Hanks earned a BS in entomology from
the University of California, Davis, in 1978, an MS in biology from the University of
Nevada, Reno, in 1982, and a PhD in entomology from the University of Maryland, College
Park, in 1991. He held a postdoctoral position at the University of California, Riverside,
and then became an assistant research entomologist there. Hanks came to the University of
Illinois in 1996.
beetles courtesy of James E. Appleby.